35 ILCS 200/21-240
Except as otherwise provided below, the person purchasing any property, or any part thereof, shall be liable to the county for the amount due and shall forthwith pay to the county collector the amount charged on the property. Upon failure to do so, the amount due shall be recoverable in a civil action brought in the name of the People of the State of Illinois in any court of competent jurisdiction. The person so purchasing shall be relieved of liability only by payment of the amount due together with interest and costs thereon, or if the property is reoffered at the sale, purchased and paid for. Reoffering of the property for sale shall be at the discretion of the collector. The sale shall not be closed until payment is made or the property again offered for sale. In counties with 3,000,000 or more inhabitants, only the taxes, special assessments, interest and costs as advertised in the sale shall be required to be paid forthwith. Except if the purchaser is the county as trustee pursuant to Section 21-90, the general taxes charged on the land remaining due and unpaid, including amounts subject to certificates of error, not included in the advertisement, shall be paid by the purchaser within 10 days after the sale, except that upon payment of the fee provided by law to the County Clerk (which fee shall be deemed part of the costs of sale) the purchaser may make written application, within the 10 day period, to the county clerk for a statement of all taxes, interest and costs due and an estimate of the cost of redemption of all forfeited general taxes, which were not included in the advertisement. After obtaining such statement and estimate and an order on the county collector to receive the amount of forfeited general taxes, if any, the purchaser shall pay to the county collector all the remaining taxes, interest and costs, and the amount necessary to redeem the forfeited general taxes. The county collector shall issue the purchaser a receipt therefor. Any delay in providing the statement or in accepting payment, and delivering receipt therefor, shall not be counted as a part of the 10 days. When the receipt of the collector is issued, a copy shall be filed with the county clerk and the county clerk shall include the amount shown in such receipt in the amount of the purchase price of the property in the certificate of purchase. The purchaser then shall be entitled to a certificate of purchase. If a purchaser fails to complete his or her purchase as provided in this Section, the purchase shall become void, and be of no effect, but the collector shall not refund the amount paid in cash at the time of the sale, except in cases of sale in error under subsection (a) of Section 21-310. That amount shall be treated as a payment and distributed to the taxing bodies as other collections are distributed. The lien for taxes for the amount paid shall remain on the property, in favor of the purchaser, his or her heirs or assigns, until paid with 5% interest per year on that amount from the date the purchaser paid it. The amount and fact of such ineffective purchase shall be entered in the tax judgment, sale, redemption and forfeiture record opposite the property upon which the lien remains. No redemption shall be made without payment of this amount for the benefit of the purchaser, and no future sale of the property shall be made except subject to the lien of such purchaser. This section shall not apply to any purchase by any city, village or incorporated town in default of other bidders at any sale for delinquent special assessments.
35 ILCS 200/21-240